Recent advances in soil microbiology and biotechnology have resulted in renewed interest to the use of microbial inoculants in agriculture, forestry and environmental management. Among the microbial inoculants, bacteria from the plant's rhizosphere and rhizoplane (rhizobacteria), are receiving considerable attention with respect to plant growth promotion. Rhizobacteria influence plant growth via different mechanisms, however, beneficial interactions are often difficult to identify and isolate for study, therefore favorable effects on plant productivity are not easily demonstrated in quantitative terms (Gaskin et al., 1985, Agriculture, Ecosystems and Environment 12: 99-116). The rhizobacteria which colonize plant roots and stimulate plant growth are known as plant growth promoting rhizobacteria (PGPR, Kloepper et al., 1988, Plant Dis 72: 42-46). Positive effects of PGPR were initially limited to root crops, like radish (Kloepper and Schroth, 1978, in Proceedings of the Fourth International Conference on Plant Pathogenic Bacteria, vol. 2: 879-882), potato (Burr et al., 1978, Phytopathology 68: 1377-1383) and sugarbeet (Suslow and Schroth, 1982, Phytopathology 72: 199-206). Later reports suggested PGPR have positive influence on diversified crops, such as bean (Anderson and Guerra, 1985, Phytopathology 75: 992-995), barley (Iswandi et al., 1987, Biol Fert Soils 3: 153-158), vegetables (Elad et al., 1987, Plant Soil 98: 325-330), canola (Kloepper et al., 1988; Grayston and Germida, 1991, Canadian Journal of Microbiology 37: 521-529; Banerjee, 1995 in Phytochemicals and Health, (Gustine and Flores, eds) pp 179-181), cotton (Backman and Turner, 1989, in Proceedings Beltwide Cotton Products Research Conference, Book 2 (Brown, ed) pp 16-17), pea (Chanway et al., 1989, Soil Biology and Biochemistry 21: 511-517), peanut (Turner and Backman, 1991, Plant Disease 75: 347-353) and many other crops. Several mechanisms have been postulated so far to explain the PGPR's positive impact on plant growth enhancement. Probably the most successful and well-known microbial inoculant for agricultural crops is that based on Rhizobium spp. through symbiotic nitrogen fixation. Kapulinik et al., (1981, Experimental Agriculture 17: 179-188) showed nitrogen fixation as a mechanism for yield increases in summer cereal crops of Israel in fields inoculated with Azospirillum. Several rhizobacteria like Azotobacter spp. are capable of producing a vast array of phytohormones (e.g. auxins, cytokinins) and enzymes (e.g. pectinase) which are intimately involved in the infection process of symbiotic bacteria-plant associations which have a regulatory influence on nodulation by Rhizobium (Okon and Hadar, 1987, CRC Critical Reviews in Biotechnology 6: 61-85). Some PGPR strains that induced yield increases of potato were reported (Kloepper et al., 1980a, Nature 286: 885-886) to produce extracellular siderophores that bind Fe3+, making it less available to certain member of natural microflora. These rhizobacteria excrete low molecular weight, high affinity ferric-chelating microbial cofactors which specifically enhance their acquisition of iron by binding to membrane bound siderophore receptors. One of the siderophores produced by some pseudomonad PGPR is known as pseudobactin that inhibits the growth of Erwinia cartovora (causal organism for soft-rot of potato) (Kloepper et al., 1980b, Current Microbiology 4: 317-320). Additions of pseudobactin to the growth medium inhibited soft-rot infection and also reduced the number of pathogenic fungi in the potato plant along with a significant increase in potato yield. Most evidence to support the siderophore theory of biological control by PGPR comes from work with the pyoverdines, one class of sideophores that comprises the fluorescent pigments of fluorescent pseudomonads (Demange et al., 1987 in Iron Transport in Microbes, Plants and Animals (Winkleman et al, eds.), pp 167-187). According to the siderophore theory, pyoverdines demonstrate functional strain specificity is due to selective recognition of outer membrane siderophore receptors (Bakker et al., 1989, Soil Biology and Biochemistry 19: 443-450). Many PGPR produce a wide variety of phytohormones (e.g. auxins, gibberellins, cytokinins) in the rhizosphere. For example, pseudomonads are reported to produce indole acetic acid (IAA) and to enhance the amounts of IAA in plants that have a profound impact of plant biomass production (Brown, 1974, Annual Review of Phytopathology 12: 181-197). Tien et al. (1979, Applied Environmental Microbiology 37: 1016-1024) found that inoculation of nutrient solutions around roots of pearl millet with Azospirillum brasilense resulted in increased shoot and root weight, an increased number of lateral roots, and all lateral roots were densely covered with root hairs. They reported that supplying the plants with combinations of IAA, gibberllins and kinetin caused increased production of lateral roots similar to that caused by azospirilla. Although the biological significance of these phytohormones and plant-hormone-like materials are not totally understood, the growth stimulating activity of these microorganisms are commonly attributed to their production of these materials. The PGPR also affect the plant growth and development by modifying nutrient uptake. The extent to which they promote uptake of mineral nutrients is a topic of considerable debate. They may alter nutrient uptake rates by direct effects on roots, by effects on the environment which in turn modify root behavior, and by competing directly for nutrients (Gaskin et al., 1985). Some factors in which PGPR may play a role in modifying the nutrient use efficiency in soils are root geometry, nutrient solubility, nutrient availability by producing plant congenial ion form, partitioning of the nutrients in plant and utilization efficiency. For example, increased solubilization of inorganic phosphorous in soil (Brown, 1974, Annual Review of Phytopathology 68: 181-197), enhanced 32P uptake in canola seedling using Pseudomonas putida (Lifshitz et al., 1987, Canadian Journal of Microbiology), and, increased sulfur-oxidation and sulfur uptake (Grayston and Germida, 1991; Banerjee, 1995). Nevertheless, factors affecting the success of a microbial inoculation or PGPR inoculation in soil include considerations at all stages of inoculum use—strain selection, culturing of the strain, carrier preparation, mixing of the culture and carrier, maturation, storage, transport and application (Killham, 1994, in Soil Ecology, pp 182-211).
U.S. Pat. No. 5,589,381 teaches the isolation of a biocontrol element comprising a Bacillus licheniformis strain which controls Fusarium seedling blight in corn.
U.S. Pat. No. 5,503,652 teaches the isolation of strains capable of promoting root elongation in plants.
U.S. Pat. No. 5,935,839 teaches the use of Arthrobacter sp. and Pseudomonas fluorescens for promoting growth of conifer seedlings wherein the PGPR are selected based on their ability to grow in cold and acidic soils typical of conifers.
U.S. Pat. No. 5,503,651 teaches the use of PGPR strains in promoting growth of cereals, oil seed crops and maize based on the chemotactic and root-colonizing capabilities of the strains.
U.S. Pat. No. 5,496,547 teaches the isolation of Pseudomonas mutants which are effective biocontrol agents against Rhizoctonia solani. 
U.S. Pat. No. 4,849,008 teaches applying Pseudomonas to the roots, plants, seeds, seed pieces or soil of root crops for enhancing the yield of the root crops.
U.S. Pat. No. 4,584,274 teaches bacteriophage-resistant Pseudomonas strains useful in promoting growth of root crops.
U.S. Pat. No. 6,194,193 teaches the use of a formulation for enhancing plant growth which comprises a mixture of Bacillus and Paenbacillus strains which produce phytohormones.
As the crop deficiencies of sulfur (S) have been reported with greater frequencies over the past several years, focused attention has been given on the importance of S as plant nutrient. In many parts in the world S deficiency has been considered as a crucial factor for adequate crop production. Especially in Western Europe incidence of S deficiency has increasingly reported in Brassica over the last decade (Scherer, 2001, European Journal of Agronomy 14: 81-111). Canola (Brassica napus L. cv) is one of the most vital oil seed crops in some of the states in US and in the prairie regions of western Canada. However, canola has the highest sulfur (S) demand of any crop grown in these region and as a consequence the yield of canola is seriously affected in soils with low S-supplying capacity. During vegetative growth canola shows very high S demand and symptoms of S deficiency can be seen when grown in most of the S-deficient soils. For example, out of 10 million acres of canola grown areas in the Canadian prairies about 20-25% lands are S-deficient. If canola is grown in those region S-deficiency symptoms will be shown and canola yield will be reduced. In order to meet the crop requirement of S and to alleviate S deficiencies in soils, various types of fertilizers can be used (e.g. sulfate forms and elemental forms of S). Elemental S fertilizer has been recommended because they are the least expensive, there are large reserves of elemental S and they are available as a by-product of the processing of natural gas. Yield response to elemental S, however, is often lower than those of other forms of S fertilizers. This is because elemental S must be oxidized to the sulfate form to be available for plant uptake. The S transformation pathway is as follows: Elemental S (S0)→thiosulfate (S2O32−)→tetrathionate (S4O62−)→trithionate (S3O62−)→sulfite (SO32−)→sulfate (SO42−). This oxidation process is largely carried out by S-oxidizers such as bacteria (most active S-oxidizer), e.g. Thiobacillus sp.; fungi, e.g. Fusarium sp.; and actinomycetes, e.g. Streptomyces sp. The forms in bold are mainly stable form and others are unstable. S-oxidizers can utilize elemental S or thiosulfate or both as their substrate for their proliferation. This rate of oxidation, however, largely depends on soil microbial activity. The nature and activity of S oxidizing microorganisms in soils has been a controversial and potential topic. Although the fundamental concept of the enhanced elemental S oxidation by the appropriate soil isolates were proven (Grayston and Germida, 1991; Banerjee, 1995) the success of utilizing the S-oxidizing PGPR in different agroclimatic condition is yet to be determined. Nevertheless, biological seed treatment of canola with naturally occurring S-oxidizing PGPR has tremendous potential to enhance canola performance with lower input cost in the canola growing areas (Banerjee and Yesmin, 2000, Agronomy Abstracts, pp 257, Annual Meeting, Soil Science Society of America). The present invention utilizes S-oxidizing rhizobacteria in canola as microbial seed treatment to enhance soil S-oxidation, crop S-nutrition and as a whole, canola performance. Thus, these rhizobacteria can be used as canola plant growth promoting rhizobacteria (canola PGPR) to enhance the canola growth, development and production.
Although PGPR may reveal huge potential for canola production, for a microbial inoculant to be commercially successful, it must be economically mass-produced and then formulated into a form that is cost-effective, uniform, and readily applicable by the end-user (Walter and Paau, 1997 in Soil Microbial Ecology: Applications in Agricultural and Environmental Management, pp 579-594). Yet, much of the research has gone into identifying and characterizing the potential microbial agent, little has been done on these aspects. According to Glass (1997 in Soil Microbial Ecology: Applications in Agricultural and Environmental Management, pp 595-618), several obstacles must be overcome to achieve the successful commercialization of these new generation products. First, microbial products are comprised of living organisms; therefore, they must be produced, formulated and sold in ways such that their viability and biological activity are maintained. Second, microbial products must compete in the marketplace with a huge number of synthetic chemicals, which are more well-known to the end-users (e.g. farmers). Finally, microbial products suffer a bad reputation based on perceived deficiencies with some earlier biological products. Moreover, the success of microbial inoculation for enhanced crop production is greatly influenced by the number of viable cells introduced into soil (Duquenne et al., 1999, FEMS Microbiology Ecology 29: 331-339) as well as biological activity may also decline rapidly with handling and storage procedure if not properly done. Thus, it is crucial to determine the duration of bacterial survivability after the bacterial seed treatment and to obtain the desired level of microbial population for the inoculant to be effective. For example, coating of bacteria treated canola seeds seals bacteria onto the seeds and prevents cells from drying out and keeps bacteria alive much longer than bare seeds. There are now other methods of delivery that are both practical and ecologically sound. But little progress has been made with alternative carriers that might enhance the numerical quality of microbial inoculants (Brockwell and Bottomley, 1995, Soil Biology and Biochemistry, 27: 683-697). Daza et al. (2000, Soil Biology and Biochemistry, 32: 567-572) evaluated a peat and a perlite-based inoculants and suggested the existence of interactions between carriers and adhesives, and showed that combination of a sucrose adhesive with the perlite carrier gave better survival of bacteria on seeds. Therefore, developing new carrier materials and/or testing of compatibility of different existing commercial inoculant carrier materials for using in the biological seed treatment is urgently needed. Moreover, additional investigation is also needed to compare pure culture strains vs complimentary mixed strains of microorganisms to form synergistic consortia that might have greater potential to give a consistent performance with better competitive ability under different environmental and growth conditions, especially in canola (Yesmin and Banerjee, 2001, in Proceedings of Saskatchewan Soils and Crops Workshop 2001, pp 314-319).
In most canola growing areas in the Canadian prairies (Saskatchewan, Manitoba and Alberta) fungicide treated seeds are commonly used as an important element to control plant diseases. These fungicides/insecticides (e.g. Vitavax RS Flowable, Helix, Gaucho) formulated as a suspension is used as seed treatment of canola to control seed decay, pre-emergence damping off, soil-borne blackleg and insect-flea beetles. It is expected that the microbial cultures (e.g. bacteria) might not survive with these pesticides at the recommended doses due to their high toxicity towards living organisms (Yesmin and Banerjee, 2000, Agronomy Abstracts, Annual Meeting, pp 257, Soil Science Society of America; Yesmin and Banerjee, 2001). Nevertheless, chance of survivability of these microbial agents may be enhanced if applied with reduced rate. As environmental concerns about groundwater quality and pesticide exposure in foods grow, biological alternatives are becoming necessary (Walter and Paau, 1997). Thus, developing biological treatment compatible to pesticides or even reducing the amount of these carcinogens could be a real boon to the agricultural industry. It is quite likely that the use of inoculants will become a routine technology in the future to increase crop production, cure problems with nutrient uptake and control of plant pathogens. But much works are needed urgently to demonstrate the mass production of inoculants, other than rhizobia, is technologically and economically viable.